In recent years there has been considerable interest and effort in connection with the development of electrically powered locks. Such locks often are designed so that they eliminate the need for the use of keys, which can be lost, stolen or copied. Keyless, electrically-powered locks provide the user with considerable convenience in their operation, as well as the required security. They also eliminate the need to replace or re-key the lock in the event of loss or unauthorized copying of the key.
Typical of a battery-powered, keyless lock assembly is the lock disclosed in U.S. Pat. No. 4,457,148 to Johansson, et al. This lock assembly employs an electromagnet which is energized upon receipt of a digital input signal having a predetermined combination. The input signal is preferably generated by manipulation of the door handle, and the manipulation of the door handle is employed to close the air gap between the solenoid and armature of the electromagnet, as well as move the bolt.
While there are numerous examples of electronic door locks which have been employed as conventional spring-biased lock sets, little has been developed in the area of electrically powered dead bolt assemblies. In a dead bolt assembly the bolt is moved positively between the locked and unlocked positions by a handle or by a key without the action of a spring or biasing means. The throw of the bolt in a dead lock assembly is usually greater than that of a spring-biased door lock, and preferably the bolt is locked or blocked against movement away from the locked position by a latching bar or lever mechanism.
Thus, even when electrically powered door locks are installed, a conventional keyed dead bolt is usually provided for additional security and strength in connection with locking of the door. Since the purpose of a dead bolt assembly is to provide additional strength, it is essential that the dead bolt assembly be constructed in a manner which does not enable an unauthorized entry by simply mechanically forcing the dead bolt assembly. Thus, dead bolt assemblies must not be constructed in a manner which will allow a burglar or vandal to obtain "purchase" or a torque applying configuration that can be used to defeat the dead bolt. Typically, spring-biased door lock assemblies are subject to override by burglars who use a pipe wrench or the like to grip the door handle and force the lock. While a conventional door lock assembly can be subject to such unauthorized entry, the purpose of having a dead bolt assembly is to maintain the door in a locked condition even when the conventional spring-biased door lock is forced open.
The requirements for a relatively long throw on the bolt of a dead bolt lock and purchase-free construction of the dead bolt assembly make electrical powering of dead bolt assemblies difficult. If a dead bolt assembly is constructed in a manner which employs electrical power to move the bolt over the long distance of a throw, it is virtually an absolute requirement that the dead bolt assembly be electrically connected to the power in the home. Thus, a battery-powered system is not suitable for a dead bolt assembly in which movement of the bolt is electrically powered. While theoretically possible, electrical connection of a dead bolt assembly to the home or office power presents substantial practical installation problems and costs.
In the electronic digital combination lock of the Johansson U.S. Pat. No. 4,457,148, a battery-powered lock is provided in which the user is able to manipulate the door handle so as to input a signal energizing the electromagnet, close the gap between the armature and solenoid of the electromagnet, and displace the bolt. Thus, the mechanical power or torque required to move the bolt and to close the electromagnet for operation is provided by the user through a handle on the exterior of the door assembly. This approach, however, provides unique problems when applied to a dead bolt assembly. It is essential, as above-noted, that the dead bolt assembly not be constructed in a manner which will allow a handle to be forced by a tool from the exterior of the door. Dead bolts typically do not include exterior handles which would enable a pipe wrench to be applied to force the lock.
Accordingly, it is an object of the present invention to provide a keyless dead bolt assembly which is electrically powered by batteries and yet is easy to use and provides the security of a conventional dead bolt.
Another object of the present invention is to provide an electrically powered, keyless, dead bolt assembly which is relatively inexpensive to construct, durable and requires minimum power to operate.
Still a further object of the present invention is to provide an electrically powered, keyless, dead bolt assembly which can be retrofitted into a wide range of installations.
Another object of the present invention is to provide a battery-powered bolt assembly and method of operation of the same in which the mechanical movement of components is effected by user manipulation of a handle in order to minimize the consumption of electrical power and yet the handle cannot be mechanically forced.
Still a further object of the present invention is to provide a dead bolt assembly which can be used with and opened by entry of a combination into an adjacent electronic door lock assembly.
Another object of the present invention is to provide an electrically powered dead bolt assembly which can be easily locked by the user without a coded input.
Still an additional object of the present invention is to provide a keyless dead bolt assembly which can be adapted for coded input as a stand-alone lock or operated as a slaved assembly in connection with another door lock assembly.
Another object of the present invention is to provide an electrically powered dead bolt assembly which is suitable for use in right-handed and left-handed dead bolt installations.
The dead bolt assembly and method of the present invention have other objects and features of advantage which will become apparent from or are set forth in more detail in the accompanying drawings and following description of the Best Mode Of Carrying Out The Invention.